Moving against the river flow, the motor ship covered 63 km in 3 hours.

Moving against the river flow, the motor ship covered 63 km in 3 hours. What is the speed of the river if the own speed of the ship is 23 km / h?

To solve this problem, we introduce a conditional variable “X”, through which we denote the river flow rate. Then, based on the data of the problem, we compose the following equation: 63 / (23 – X) = 3. Solving this equation, we obtain 63 = 3 (23 – X) or 21 = 23 – X or X = 23 – 21 = 2 kilometers in hour.
Answer: the speed of the river is 2 kilometers per hour.